1. Field of the Invention
The present invention relates to an interchangeable medium data storage apparatus for reading data after the loading of an interchangeable medium.
In recent information processing systems constituted of a host apparatus equipped with an interchangeable medium data storage apparatus, there are demands for high-speed access between the host apparatus and the storage apparatus. For this reason, it is requested that data is read at a high speed after a medium is loaded, irrespective of the type of medium or the type of OS (operating system).
2. Description of the Prior Art
In storage apparatuses such as a magnetic disk apparatus, an optical disk apparatus and a compact disk read-only memory (CD-ROM) apparatus, wherein the medium is interchangeable, there is created a time in which the storage apparatus waits for a command from the host apparatus after defect management information and the like are read from a medium loaded in the apparatus. Any process is started only after the command is received.
That is, in a computer system incapable of automatically recognizing the mounting of a medium, the medium cannot be accessed until an operator performs a file access after the medium is loaded. When the operator requests an access to a file on the medium, the OS first reads system management information and then carries out a process relating to a file operation requested by the operator.
According to some OSs, the host computer issues a predetermined command at regular intervals, and a process (such as reading of system management information) relating to the command is executed after a medium is loaded.
FIG. 1 is a flowchart of a conventional process carried out when a medium is loaded in a storage apparatus. Referring to FIG. 1, when the power is turned ON or a reset operation is initiated (step S201), a determination is made using a sensor equipped in a medium loading mechanism as to whether or not a medium is inserted into the storage apparatus (S202). When it is found that the medium is not inserted, a determination is made as to whether or not a command is issued (S203). When it is found that a command is issued, that command is processed (S204).
When it is found that a medium is inserted, a medium loading process including the driving of a spindle motor into rotation is performed (S205). A determination is made as to whether or not the medium is ejected, or whether or not there is an instruction to eject the medium (S206). When there is an instruction to eject the medium, the medium is ejected (S207).
When the medium has not been ejected, a determination is made as to whether or not the host apparatus issued a command (S208). When it is found that no command is issued, the storage apparatus waits for a command. When a command is issued, a determination is made as to whether or not the issued command is a read command (S209). When the issued command is not a read command, that is, for example, when the issued command is a write command, an associated command process such as a writing process is carried out (S210), whereupon the control is returned to step S206.
When the issued command is a read command, that is, for example, a read command for reading OS management information, a read process performed such that a read head is positioned to an address specified by the read command, data is read and stored in a buffer, and the data is transferred from the buffer to the host apparatus (S211). The control is then returned to step S206.
In this way, the OS management information or the like is read only after a read command is issued from the host apparatus.
The prior art described above is characterized by a slow response to an access from the host apparatus because a mechanical operation including a seeking operation of the head is carried out after a read command is issued from the host apparatus after the medium is loaded. Hence, the prior art has a problem in that a speedier access cannot be attained. The problem is particularly noticeable in an optical disk apparatus because adjustment of an optical head including an adjustment of an optical power, tracking and a focusing is required after the medium is loaded.
There are some known methods designed to attain a high speed access between the host apparatus and the storage apparatus, including the methods disclosed in Japanese Laid-Open Patent Application No. 62-27446, Japanese Laid-Open Patent Application No. 1-166240 and Japanese Laid-Open Patent Application No. 1-122488.
Japanese Laid-Open Patent Application No. 62-27446 discloses a method whereby a non-resident program is read in accordance with a command from a central processing unit (host apparatus) at the start of the system and transferred to a memory circuit constituted of a random access memory (RAM). According to this method, a seek operation and the like are performed only when a command from the central processing unit is received after the loading of the medium, resulting in a slow response to an access performed after the loading of the medium.
Japanese Laid-Open Patent Application No. 1-166240 discloses a method whereby a program stored in a non-volatile memory (magnetic disk) is transferred from the non-volatile memory to a main memory without being routed to a work memory (buffer). In accordance with load information file read from the non-volatile memory. Like the conventional method described above, the seek operation and the like are performed only after a read request for the load information file is issued, resulting in a slow response to an access after the loading of the medium.
Japanese Laid-Open Patent Application No. 1-122488 discloses a method whereby data in a predetermined address is read when the disk is loaded. The seek operation and the like are performed by access means in response to a read command from the host system. There is a problem in that a certain period of time is wasted in waiting for a command and a time is further required to issue the read command. An additional problem with this method is that it is impossible to adapt to a change in a medium format etc. or a change in the operating system.